Real-world analog signals such as temperature, pressure, sound, or images are routinely converted to a digital representation that can be easily processed in modern digital systems. In many systems, this digital information must be converted back to an analog form to perform some real-world function. The circuits that perform this step are DACs, and their outputs are used to drive a variety of devices. Radio frequency (RF) transmitters, loudspeakers, video displays, motors, mechanical servos, and temperature controls are just a few diverse examples. DACs are often incorporated into digital systems in which real-world signals are digitized by analog-to-digital converters (ADCs), processed, and then converted back to analog form by DACs. In these systems, the performance required of the DACs will be influenced by the capabilities and requirements of the other components in the system. Present day DACs are becoming increasing sophisticated as the range of applications for digital circuits increases.
Many architectures exists for DACs, including delta-sigma DACs, R-2R DACs, string DACs, and current steering DACs. These architectures have varying advantages and disadvantages. For high-speed or high converter/sample rate applications, current steering DACs tend to be the best among the different architectures. Current steering DACs, have been moving to higher and higher sample rates as companies push to achieve high instantaneous bandwidth. The requirement of instantaneous bandwidth comes with the additional requirement that dynamic performance should not be sacrificed relative to existing lower bandwidth, lower frequency solutions. For instance, it is desirable to reduce distortions in high speed current steering DACs, but reducing distortions is not trivial.